From: "Yury Norov (NVIDIA)" <yury.norov@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
linux-kernel@vger.kernel.org
Cc: "Yury Norov (NVIDIA)" <yury.norov@gmail.com>,
Markus Elfring <Markus.Elfring@web.de>,
Madadi Vineeth Reddy <vineethr@linux.ibm.com>,
K Prateek Nayak <kprateek.nayak@amd.com>
Subject: [PATCH RESEND] sched: fair: drop useless cpumask_empty() in find_energy_efficient_cpu()
Date: Sat, 6 Dec 2025 23:05:42 -0500 [thread overview]
Message-ID: <20251207040543.407695-1-yury.norov@gmail.com> (raw)
cpumask_empty() call is O(N) and useless because the previous
cpumask_and() returns false for empty 'cpus'. Drop it.
CC: Markus Elfring <Markus.Elfring@web.de>
Reviewed-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
---
Rebased and re-tested on top of master. Original patch:
https://lore.kernel.org/all/20250911023426.457745-1-yury.norov@gmail.com/
kernel/sched/fair.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e04f94233cda..af9e9dbdaa6d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8362,9 +8362,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
int max_spare_cap_cpu = -1;
int fits, max_fits = -1;
- cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask);
-
- if (cpumask_empty(cpus))
+ if (!cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask))
continue;
/* Account external pressure for the energy estimation */
--
2.43.0
next reply other threads:[~2025-12-07 4:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-07 4:05 Yury Norov (NVIDIA) [this message]
2025-12-08 8:50 ` Peter Zijlstra
2026-01-12 8:03 ` [tip: sched/core] sched/fair: Drop " tip-bot2 for Yury Norov (NVIDIA)
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